Method of forming a strongly adherent electrodeposit



Dec. 12'. 195 w. B. STODDARD, JR 3 METHOD FORMING A STRQN ADI-IE T ELEGTRODEPOSI Filed Jan. 8, 1946 4 Sheets-Sheet 1 Dec. 12, 1950 w. B. STODDARD, JR 2,533,533 METHOD OF FORMING A STRONGLY ADHERENT ELECTRODEPOSIT Filed Jan. 8, 1946 4 Sheets-Sheet 2 f" 10 mix)! IN VEN TOR.

mmgo w Dec. 12, 1950 w. B. STODDARD, JR 2,533,533

METHOD OF FORMING A STRONGLY ADHERENT ELECTRODEPOSIT Filed Jan. a, 1946 4 Sheets-Sheet s Dec, 12, 1950 w. B. STODDARD, JR 5 9 METHOD OF FORMING A STRONGLY ADHERENT ELECTRODEPOSIT Filed Jan. 8, 1946 4 Sheets-Sheet 4 E i9. l .7

Patented Dec. 12, 1950 METHOD OF FORMING A STRONGLY ADHERENT ELECTRODEPOSIT William B. Stoddard, Jr., Hamilton, Ohio, assignor to The Champion Paper and Fibre Company, Hamilton, Ohio, a corporation of Ohio Application January'S, 1946, Serial No. 639,870

Claims. (Cl. 204-46) This invention relates to the electrodeposition of metals-onto a metallic base and is herein more particularly described as applied to the electrodeposition of nickel onto surfaces composed partly of nickel and partly of solder. It involves the preparation of these surfaces in a manner such that the poisoning effect of the solder on adjacent parts of the base metal surface is prevented, and the bond between the electrodeposit and the base metal has strength comparable to that of the base metal itself. It has especial value where the electrodeposited metal is not to form a mere decorative or protective coating, but instead Where it and the base metal are to constitute parts of an integral mechanical structure. It has a particular utility in cases where a body of solder or the like, constituting a material part of the surface onto which a layer of metal is electrodeposited, is to be subsequently removed by fusion or otherwise to leave an integral structure composed in part of the base metal and in part of the electrodeposited metal.

In the electrodeposition of metals such as nickel, it is known that the presence of solder on or adjacent to the surface onto which the deposit is to be made, poisons the surface, preventing a tightly adherent deposit in the vicinity of the solder. It has consequently been common practice in nickel plating objects having soldered joints or the like, to first flash plate the object with copper in a cyanide bath; then, after base metal and solder were covered with a coating of copper, to carry out the nickel plating operation. This expedient produced a plate of substantially uniform appearance over base metal and solder, and normally served to prevent spontaneous peeling of the nickel plate from the solder or the base metal and was generally considered adequate for the provision of decorative and protective coatings. However, in cases where the deposit is required to be strongly adherent, as where the deposited metal is to form a stress carrying part of a mechanical structure of which the base metal forms another part and stress must be transmitted from one to the other, this method is found to give completely inadequate adherence. No matter how perfect the electrolytic bond between the base metal and the copper and between the copper and the electrodeposit thereon, the bond can be no stronger than the copper link which, when it joins metals such as steel and nickel, possesses but a fraction of the strength of the metals joined. In practice, however, the strength of the bond between the base metal and the electrodeposit has been found to be much less than that of the copper link, indicating that the presence of solder has poisoned the base metal against the deposit of copper, as against the deposit of other metals. Further, this poisoning effect of the solder appears to become more serious and harder to combat as the surface area occupied by solder becomes larger in proportion to the entire area of the surface onto which the electrodeposit is to be made.

I have now discovered that solder can be prevented from poisoning adjacent nickel surfaces if, instead of attempting to cover or otherwise to protect the surface of the nickel per se, the surface of the solder, rather than that of the nickel, is protected by completely covering it with a suitable film during the time prior to the beginning of electrodeposition thereon during which poisoning otherwise takes place, while the surface of the nickel is free from anything which might interfere with strong adherence between it and metal electrodeposited thereon. Since it is generally desired to electrodeposit metal over both solder and nickel surfaces, the film formed over the solder must be electrically conducting, when submerged in the plating bath, to the extent that it does not materially interfere with the electrodeposition of metal over surfaces covered thereby. In order to give the best results, the film should be substantially continuous and impervious and should substantially completely cover the surface of the solder, should be resistant to solution in water, and should resist solution in, and penetration or removal by, the plating solution, so that it forms a physical and chemical barrier separating the solder from the plating solution.

I have further discovered that such a film can be formed on and confined to the surface of the solder by use of electro-chemical reactions which involve metals present only in the solder. The particular reaction which I have found most effective in the formation of such films on solder is anodic treatment in a concentrated solution of sulfuric and phosphoric acids.

I have additionally discovered that when surfaces composed partly of nickel and partly of solder are given this anodic treatment to form a protective film over the surface of the solder, no further treatment of the nickel surface is required to so prepare it for the reception of a deposit of nickel that the bond between the base metal and the deposit will be substantially as strong as the metal itself.

This method of covering the surface of the solder with an electrically conducting protective film and simultaneously preparing the nickel surface to receive a strongly adherent electrodeposit may be carried out a follows: The combined nickel and solder surface may first, if necessary, be cleaned as for example by treatment as cathode in a usual alkaline cleaner. It is then immersed and made the anode in a concentrated solution of sulfuric and phosphoric acids, or of sulfuric acid and other tribasic acid, at a temperature ad-, vantageously between about 30 and 45 degrees C., though the process appears to be operable over a considerably wider temperature range. The cathode may be of any suitable material, e. g. lead, which is not too seriously attacked by the acid bath. When the film over the solder has reached the required thickness, the current is turned off and the treated surface is removed from the bath and thoroughly rinsed with water. This rinsing appears readily to dissolve or otherwise remove any film or deposit which. the elec-- trolytic action may have formed on the nickel parts of the surface, but has no apparent effect on the film formed on the solder parts of the surface. The treated part is then made the oathode in a nickel plating bath and deposition is carried out inthe usual manner. Since the film isonly efiectivefor a-limited time in the plating bath, it is desirable to avoid unnecessary exposure to the plating bath with the current 011. Also-,gsolder flux inclusions and foreign matter accessible from the surface may cause non-ad herence and should be carefully avoided.

If the preparation hasv been carefully carried out inthe man-her describedit is found, contrary to the usual experience with electrodeposi- 1110?; following anodic treatment of nickel, that the electrodepositadheres to the nickel base with strength'substantially equal to that of the nickel itself. This degree of adhesion appears to ex-' tend over the entire area of the nickel surface up to, or substantiallynp to, its junction with the solder surface, thus demonstrating the effectiveness of this method not only in preventing the poisoning eifect of thesolde'r on the nickel parts of the surface but also in preparing the nickel surface for the reception of a strongly adherent electrodeposit. t

it is not to be understood that the film over the surface of the solder prevents adhesion of the electrode'posit to the solder, as the adherence here appears to meet the usual commercial requirements foradherence of electroplate. This is, however, of little interest in cases where this process is used. to build up a mecl ia-nical strucacids. Bath compositions are herein defined in proportions by volume of sulfuric acid 1:83 specific gravity, phosphoric acid of 1:689 specific gravit, and Water. The proportions of these const ituen'ts' do not appear critical and mayvary considerably. Water'is advantageously not much over sixty per cent and may be as little as ten *per cent or less. Phosphoric acid should be present-fn'a reciable amount say one per cent or more. The ratio of phosphoric to sulfuric acid 4 is advantageously from one-third to one-half but may vary from less than one-tenth to more than one. A generally satisfactory solution, using acids of the strengths already noted, may be made up of 60 parts of sulfuric acid, as parts of phosphoric acid, and 20 parts of water, by volume.

Polarization phenomena naturally cause a material diiference between the current densities on the solder and non-solder parts of the surface. The only current density which can be determined is, therefore, the average current density over the entire area, and when, as is frequently the case,- solder forms a material portion of the surface being treated, this average is meaningless unless the proportion of the area covered by solder and the efiects of polarization on both parts of the surface are definitely known. For this reason it is generally more satisfactory to maintain the voltage, rather than the current density, at a need value, for example about 7.5 volts. While voltages materially higher than this value may be used, I have ingeneral secured more satisfactory rea ts at about the voltage named At lower voltag as from about 4 to 6 volts, the current how frequently appears to be unstable. Such lower voltages should, therefore, be used with caution if at allt I have further found it advam ta'geous many cases to follow this with trean nie'nt at a reduced voltage, e, 3 volts, fora short time, since at this voltage a reddish brown film is reins-ed on the surface of the nickei, where it is in coi iditio'n to receive an adh l nt "elec trodeposit, this constitutes a @dverlierit visual indicator showing satisfactor preparation. A strong Odor "Of -0Z'Gf'1 has also be'fllfS'el-V-Qd successful operation of the anodizing step in the pr'ocessi so far the process has been described as applied to the electredep'osition of nickel onto surfacescornposed in part of nickel and in part of solder. I have found, however, that it is more broadly useful. The presence of solder does not appear to be necessary to the-effectiveness of this treatment in securing strong adhesion of nickel deposits to a nickel base. Further, the process as described can be successfully usedo-n a metallic base of either steelor nickel, in the presence of solder; and willserv'e to prevent the usualpoisoneffect of the solder and will-at the same time prepare-the base metal for the reception of an eleetrodeposit "of iron or nickel which *will then adhere to the base metal with strength substantially equal to that of the metals themselves. With steel, however, the anodizing solutions are advantageously lessdilute'than can be used with nickel.

In thiscoimectio-n, the term steel as herein used includes carbon steels in all usual ranges" down-to andiricluding the extremely low carbon steels-sometimes referred to as ingot iron. It also includes the so' called low-alloy steels suhas those containing nickel, chrome -nickel, chrome= nickel-molybdenum, etc. in which none of the allo ing elements is present in excess of three to five per cent. It specifically does not include 'the'high-alloy steels commonly known as stain less steel, such "as for example the 18:8 steel of commerce; The process as defined has been found to operate successfully on the ty es of steel included in this definition and to be unsatisfactory as a final preparation for the reception of an adherent electro-deposit'on the types of steel herein excluded from'the meaning of the term. Th'e't'erm iron is herein'used with reference to electrolytic iron as distina guished from the usual commercial form of iron and steel. The term nickel is to be understood as re ferring not only to pure nickel but also to nickel containing minor percentages of cobaltan element. which is commonly present, to a greater or lesser extent in commercial nickel. anodes.

The term solder as herein used includes metals and alloys consisting largely, of lead and/or tin. Pure lead alone is operative, as is also pure tin.. In many respects the most satisfactory alloyv from the standpoint of this process is. the eutectic alloy composed of approximately 68 parts tin and 32 parts lead, though alloysof widely varying proportions can be successfully handled by the process hereinbefore described. The rinsing step described as following the anodizing is generally. recommended though-not always necessary. When using anodizing solutions containing phosphoric acid, it is. desirable to rinse with water to keep the phosphate radical out of the plating bath. In case of nickel plating baths containing boric acid, any boric acid carried over from an anodizing bath containing boric instead of phosphoric acid, is harmless. In such case no rinse appears to be neces sary, agitation in the plating bath apparently having sufficient solvent or rinsing action to remove any harmful film from the surface of the nickel before electrodeposition is begun, if any such film has in fact been left by the anodizing step.

The invention will be made more clear by the description of illustrative embodiments with reference to the accompanying drawings, in

required to receive an adherent electrodeposit.

Fig. 2 is a similar view showing the same portion of the surface after the formation of a film over the surface of the solder.

Fig. 3 is a similar view illustrating in dotted lines the reddish brown film which -may be formed, if desired, over the surface of the nickel, by brief anodization at reduced voltage, in order to form a visual indication that the preparation for electrodeposition has been completed.

Fig. 4 is a similar view showing the same portion of the surface after the electrodeposition of metal thereover.

Figs. 5 to 11 inclusive, show the adaptation of the process to the patching of a hole in sheet metal as described in Example 2, Fig. 5 being a cross section of a part of a metal sheet at a hole. Fig. 6 is a similar sectional view after a stainless steel sheet has been soldered over the hole. Fig. 7 shows the same after mechanical preparation and the cementing of the electrolytic cell in place. Fig. 8 shows the same after the anodic treatment. Fig. 9 shows the same after filling of the hole with nickel. Fig. 10 shows the same .after removal of the stainless steel and'solder.

11 shows the finished patch after the electrodeposited nickel has been dressed down to the level of the sheet.

- Figs. 12 to inclusive, show the adaptation of the process to formation of a structure as described in Example 3. Fig. 12 is a fragmentary cross sectional view through the two sheet metal struts embedded in lead. Fig. 13 shows the same after anodic treatment. Fig. 14 shows the same after deposition of iron over, the anodically treated surfaces. .Fig. 15 shows thesameafter the melting out of the lead. x.

Figs. 16 to 19 inclusive, show the adaptation of the process to the formationof a structure as described in Example 4. ,Fig. 16 is across sectional view of the solder-filled base before treatment. Fig. 17 shows, the same after anodic treatment; Fig. 18 shows the same after the deposition of nickel over the anodically-treated surface. Fig. 19, shows the, completed structure as it appears after melting out the solder. Referringfirst to Fig. 1,- the smooth metallic surface In is partly composed of solder H :and partly of another metal l2 which may for-purposes of illustration be considered to be nickel. In order to prevent the presence of the solder II from poisoning the adjacent portions of the surface [0, to a greater or lesser distance from the solder H, against the reception of an adherent deposit of nickel, the exposed surface of the solder is covered by a film l5 v(Fig; 2) advantageously by anodic action in a bath. of concentrated sulphuric. and phosphoric acids in the manner already described. This film (the thick ness of which is greatly exaggerated in the drawing) should as nearly as possible completely cover the solder and be sufliciently inert and impervious to prevent the solutions used from contacting the solder prior to the formation of the ,electro:- deposit thereover. Conversely, the film should, advantageously, cover only so much of the. S111:- face as is composed of solder since, if.it covers more, the area of strong adherence is corree sponding-ly reduced, and if used in a stress-carrying structure, points of stress concentration which may lead to failure are introduced. This film, in order that the electrodeposit maycover the entire composite nickel-solder surface, must be electrically conducting to an extent that it does not appreciably interfere with the electrolytic deposition of nickel thereover.

"After the solder is covered by film IS the surface is ready to be placed in the plating bath and to receive the required electrodeposit. It is, however, in some casesconvenient to con clude anodic formation of the film with anodic treatment at a reduced voltage, as alreadydescribed, inorder that a visible reddish brown film may be formed over the nickel surface" to serve as a visual indication that the surface, is prepared to" receive the electrodeposit. This film is illustrated at It in Fig. 3, by dotted lines, to indicate the fact that it is not a continuous impervious covering as is film 15' but that it is ap, parently discontinuous or at least so non-adherent or evanescent that it apparently disap pears in the rinse or in the plating solution itself before deposition begins.

The body with the surface prepared as shown in Fig. 2, orwith the additional film l6 as shown in Fig. 3, is then introduced into the plating bath, as described, and covered with an electrolytic deposit I! (Fig.- 4) of nickel of any specified thickness. As shown in the figure there is no sign of any film it between the nickel base I! and the nickel deposit 11, regardless of whether or not it was formed on' the surface prior to electrodeposition. The adherence of the deposit I! to the base !2 is, if the process has been care?- fully carried. out as described, of a strength approximately equal to that of the nickel itself, so that any stress may be transmitted through the bond I 2 and I! which could safely be transmitted by the weaker of the metals l2 and I! (if not of identical strength). As indicatedip.

the fie'ure howeverz the layee fi remains betweerr the solder H and the 'electrodeposit;H in the. finishedstructure. Inspite-of thisiace the adhesion betweenthe 'deposit I'l and: the solder portion l-l= ofethe base appears-to-beas-great as thatqisuall y required'in electroplatingoperations; lit-cases; however, where a-stress-carrying structure is; being; produced; the solder itseli has, relative" to; the' nickel, so=- li-ttle-- strength: that neither; itsstrength-non the; strength of bond-be:- tween it and deposit. this-considered; Lhis is: particularly true in those:- cases where the solder H is merely-a 'iormior giving shape to apbody" eleotroformed-thereover, and is=subsequently re-'-. mqyed by fusion.

A clearunderstanding. of facilitated;by,- the following examples of. the S110! cesstul use thereof:

x ple-l 1 .A' surface, some; 180;- square inches; in-,=extent,, of; electnoformedf nickel J sheet-.havingz: atensile strength ofxover. 100,000, pounds.,.per -i squareinch; wasnushwith a.surface:-. of: solder; composed: of lead. and. ting in; substantiallv.- eutectice pro: liqltiong. so formed the line ..of-: contact; between .nioke-li andisolder was approxie mateln 150 inches. in.;1ength., Without-any pre: liminary..- treatment= thisnickel: and; solderwsurfacet-was treated anodicaliyi in: a solution 7 of 1 60A pasts su fu c: acid; 23).: parts. phosphoric: acid; and-n20 partsrofiiwateri maintained at: a tempera, turaoflabout-itfifi-G: 'liher-appliedalpotential;was: T /zsvoltst for; theszfirst .threasminutes; a'i ten-whi xll, lttwasereduced .to'.3 :vo1ts andzthe; treatmenteon-l. tinned... ion three more; minutes. By this; time thee: nickel parts; 015' the surface could. be seen to be. vcovered with a: reddish'cbrow-n film, which was; however; removed-.1 in. the next; stone-the rinsing: of: the; surface. for. minutes in; run;

by: tests. of" the. strengths of the bond between: the

nickeldeposit: and thehnickelibase; These; tests; carried: out: after remova-lr of; the i solder; showed the bond between the. electrodeposits. and: the nickel base to. have. substantially the same strengthas the. base sheetitselh No evidence of: the usual: poisoning effect? of? the solder "on the adherence of the deposit to. adiacenta parts Ofit1I8-:.I1i0k81r surface; was "detected;

mmplerl n; t ase.- the n ion-i wa adap az a a cess f: mach neole nvshe ts rip o nickel and madeuseof; h r in eioratat d fact; that the anodicmethod of; formingga film oven: the surface of; the soldeiv does;- not; leaye stainless steel ;-in-: the presence ofssolder inzaa on clition:v to lreceive: an adherent electrodeposit ofiren" o-ieni-ckel: ItiWfiSsdBS-H'Bd to. patchnaehole 24 about one. inch in: diameter inw a sheet' fli' of nickel 'about. 01110 men thick A pi i tamtheprocess will? be less steelaizs smear was soldered;- byi. meansaot solder 26 onto one side of the nickel ShBRtG'CQYeE'm ing the hole. The edgesotnthehole were bevelled. as shown at '25 and: the solder was cleaned offi' ot-the stainless steel. This-process resultedinabevelled annularsurface of nickel: 25a anda;

bevelled: annular surface-of" solder 26; surrounde ing aflat: circular surface 21- of stainless. steel and surrounded byjftheflat. surface of: the nickel: sheet 12* Asmall electrolytic cell the lower 'part, of which. is indicated at 31 with an open bottom was set upover: the-prepared. hole: and cemented in place sis-indicated; 842.32; A: solution of, 60;.

parts sulfuric acid, 20. partsphosphoricvacid. and ZQN-partswater was placed the cell. and1 the; preparedasurfacevwas made anodeaat a. potential ofa'i /g -ivoltsrior 3im-inutes, followed by: a potential of 3s. vpltssfor: 3; more; minutes, after which; the nickel;. parts. of the.- surface were covered with a reddish brown. filnrindicatedbp the .dotteddine It, and; the: solder: was covered by;- theepr yi uslic describedianodic nlmllet Thesomtionwast en. removedzlfrom. theacell andthean dizsd 9? and: interior: ofrthe cell were, thorough-1 rinsed, with water.- Anickel platin solution. w a he placed in the; cell, and; provisiQIi-S. were; made, for m n ainin a ntinuous; circulation-of the r so; luticn through the. cell from. a larger; reservjq n and nickel was depositedionto the. prepared. sur: ace until; the deposit; had rea hed a; his mess; definitely; greater than the thickne s of. the sheet plus that of the solder. The work wa-s the r. hea edto use th olde stainle steel bass net. wasthenr ead ly. .removemvloas ns the hatched; heet. n: he; c ndit n: llustra ed in Fig. 10, the anodic treatment having leitfits surface n. a- Qnditio hatthe nipk l ele trodenos t d hereon. d, ot adh rehtly hereto v Th p tch w s lieni r eddowna to he hickness nd su efi ishof the dia ent parts of theniclgel sheet. The; patch was then a; sub tan iallr nd st ngu h b e P rt. of the original sheet as indicated in Fig lltwhereinthe eleQtlfO d eposited5 patch; 35; and the original sheet 2' oss hatched in: pposi e; di c i ns, t indicate their, distinct origins, but are notsep: arated bx any line, thus indicating, that. they are completely homogeneous andin efiect asingle piece;

Example 3:

In this case separate members 41 and 42 formed oi a 16 gage sheet of galvanizing rade ingot'iron were embeddedin lead 43'with bent over flanges 45 and 46' ofrthe sheet members lyingflushwith the surface f'the lead: Of the entire surface treated; approximately '7 per cent wasironand 93 per cent was lead: This surface; afterthe known process of cathodic alkalinec-leaning was treated asanode in a, solution of parts sulfuric acid, 20 partsphosphorio acid; and-20 parts water, at: a potential of'7.5 volts; as described; for a timeof about lo-m-inutes. This left the surface0f the-lead 43 covered with the anodic film-l5 as illustratedin Fig: 13." Theflanges tfi and 46-? on members 44 and- 42; being; of iron; the reddish brown' film l5,- found in the previous example, was not formed thereon, the-surfaces of flanges 45 and 46 being left exposed bythe anodic treatment andina condition toereceive a strongly adherent electrodepositi It was then thoroughly rinsed with water: and Iiron .was elec trodeposited thereon; in accordance. with the process describedin my co -pending. application for patent Serial No. 477,131 filed-February. 2.5,

1943, now Patent No. 2,420,403, until a deposit 41 of approximately 0.050 inch thickness was secured on each side thereof as illustrated in Fig. 14. Thereafter the lead was melted out leaving a structure formed as illustrated in Fig. 15 of electrolytic iron flanges 41 joined by rolled sheet iron webs and struts 4| and 42. Tests to destruction showed electrolytic iron 41 and bonds between it and the rolled section 45 and 46 to be of such strength that failure took place in the rolled metal itself rather than in the electrolytic metal or the bond.

Example 4 The base metal was S. A. E. 4340 stee1-a i medium carbon low alloy chrome-nickel-molybdenum steel in which none of the alloyin elements are present to an extent greater than 2%-- hardened and heat-treated to develop maximum toughness and shock resistance. The body on which the deposit is to be made is illustrated in Fig. 16, which shows the steel portion 5! and the solder portions 52, 52. The entire superficial area on which the electrodeposit was to be made was approximately 140 square inches, and of this, 60 square inches or roughly 43% was composed of solder. The solder surfaces composed the major part of one face of the object except for narrow borders 53 and a central strip 54 about A; inch in width where the surface was of steel flush with the surface of the solder. The entire object was electrolytically cleaned as cathode in an alkaline solution in a -well known manner. After rinsing, it was treated anodically in a concentrated solution of sulfuric and phosphoric acids of the composition previously described, using a potential of 7 volts for a period of 20 minutes, in the manner hereinbefore described. This treatment left the anodic film 85 (the thickness of which is greatly exaggerated in the drawing in order to render it visible) covering the surface of the solder 52 as illustrated in Fig. 17. The surfaces 53, 54, and 55 of the steel were left without any film and in condition to receive a, strongly adherent electrodeposit. The entire object was then rinsed and immediately thereafter it was nickel-plated under conditions adapted to yield a deposit of about 120,000 pounds per square inch tensile strength, until the nickel deposit 51 has reached a thickness of approximately 0.060 inch. The body then appeared (in section) as illustrated in Fig. 18, wherein the electrodeposit 51 is distinguished from the steel base 5! merely by direction of cross hatching and is not separated therefrom by a line. This is done to indicate the fact that the electrodeposit El'and the steel base 5| are substantially integral and cannot be separated or peeled off as is sometimes the case with common electroplate. The assembly was then heated to about 400 F. until the solder melted and flowed out leaving a large cavity 58 on each side of a central steelpartition, as illustrated in Fig. 19 between a relatively heavy steel back and a 0.060 inch thick nickel cover. The structure was then tested to destruction. The steel back and nickel cover wereboth badly deformed and rupture occurred both in the steel and in the nickel but nowhere in the joint between steel and nickel. The 0.060 inch nickel sheet was completely torn from each side of the strip of nickel which remained firmly adhering to the 4 inch wide steel surface at 54 which originally separated the two parts of the solder p area-showing a conspicuous absence of the usual poisoning effect of the solder on the adjacent surfaces of the base metal.

Example 5 The base metal was again S. A. E. 4340 steel. About 6 per cent of the area of the surface to receive the electrodeposit was formed of solder composed of 2 parts lead and 5 parts tin. The anodizing bath was composed of 60 parts sulfuric acid, parts phosphoric acid, and 20 parts water. This bath was maintained at a temperature of 35 to 42 C. A lead cathode was used while the surface to be treated was made anode using an average current density slightly less than 2 amperes per square inch for a period of approximately 10 minutes. Thereafter the part was rinsed and placed in a nickel plating bath and nickel was deposited thereon until base metal and solder were covered with a layer about 0.040 inch thick. The adherence to the base metal was of strength approximately equal to that of the nickel itself and this degree of adherence extended up to the very edge of the solder.

Example 6 In this example the base on which the nickel was deposited was S. A. E4340 steel, with 6 per cent of the area to be plated composed of solder consisting of 2 parts lead and 5 parts tin. The procedure was the same except that the anodizing bath in this case was composed of 50parts Example 7 In this case the base metal was S. A. E. 4340 steel. About 6 per cent of the area of the surface was formed of solder composed of 2 parts lead and 5 parts tin. After a usual cathodic alkaline cleaning operation, the surface, composed partly of steel and partly of solder, was treated anodically in a bath composed of '70 parts sulfuric acid, parts Water, and enough orthoboric acid to saturate the bath. The temperature of the bath was to 44 0., the potential 7 volts, and the average currentdensity was 0.9 ampere per square inch. The anodic treatment was continued for a time of 10 minutes. After removal from the anodizing bath, and without the necessity of preliminary rinsing, nickel was electrodeposited thereon until the deposit had reached a, thickness of about 0.035 inch. The deposit was found to adhere to the steel with a strength approximately the strength of the nickel itself.

Example 8 In this case the base metal surface was about two-thirds hard electrolytic nickel and one-third solder. The anodic treatment was carried out in a solution composed of 50 parts sulfuric acid, 5 parts phosphoric acid, and. 45 parts water. This bath was used at about room temperature with an average current density of about 200 amperes per square foot for about two minutes. After this treatment the surface was rinsed with water and an e ectrolytic deposit of nickel was made thereon, the application of the plating current being simultaneous with the contact of the process described in promoting strong adherence and preventing the usual poisoning erfect of me vtalliclead or tin as well as of solder, all of which normally .cause non-adherence or weak adher- Jence ofiron or nickel electrodeposited onto surfaces of nickel or steel when these are .adjacent to.-surfaces composed of .the solder, lead, or tin.

I claim:

.1. In preparation for the electrodeposition of nickel .onto a metallic surface composed in part of solder and part of a metal chosenfrom the class consisting of steel and nickel, the step of forming on and co-extensive with the surface of the solder, by making the surface anode in a concentrated aqueous solution of sulphuric acid and phosphoric acid an electrically conducting film which is resistant to penetration or removal by the plating solution.

2. In preparation for the'electrodeposition of metal onto a metallic surface composed partly of a metal chosen from the class consisting of steel and .nickel and partly of solder, the step of anodically forming in a concentrated aqueous solution of sulfuric acid and an acid containing three replaceable hydrogen atoms, chosen from the class consisting of phosphoric acid and boric acid, on and co-extensive with the surface of the solder, an electrically conducting film which is resistant'to penetration or removal by the plating solution.

'3. In preparation for the electrodeposition of metal onto ;a metallicsurface composed partly o'f.:a metal chosen'from theclass consisting of steel and nickel and partly of solder, the step of anodically forming,inaccucentrated aqueous solution of sulfuric and phosphoric acids containing not less than one percent of phosphoric acid, on and co-extensive with thesurface of the solder, an electrically conducting film which is resistant to penetration or removal by the plating solution.

.4. The method of forming a strongly adherent velectrodeposit of ,a metalchosen from the class .consisting of iron and nickel onto the surface of a metal chosen from the class consisting of .steelcand nickel inthe presence of solder, which comprises: completely covering the surface of the solder by anodic treatment of the composite surface,usingpotential between about 6 and 9 volts, at .a temperature between about .30 degrees and 45 degrees C. .in a concentrated aqueous solution. of sulfuric and phosphoric acids containing .not less than one percent of phosphoric acid, with a vco-extensive, electrically conducting film which is resistant to penetration or removal by the platingsolution; rinsing the parts with water; and thereafter electrolytically depositing said chosen metal over said metallic surface including'thefilm on the solder.

5. The method of preparing the surface, which 7 is liable to poisoning against the reception of an adherent electrodeposit, by the "presence of solder thereon, vof-a metal chosen from the class consisting of steel and nickel for the'reception of an adherent 'electrodeposit of a metal chosen from the'class of iron and nickel, which C0111" prises subjecting the surface to treatment as anode ina concentratedaqueous solution of sul .furic .acid and an .ac-idcontaining threereplaeeable hydrogen atoms, chosen ..from the class consisting of phosphoric ,acidand .boric ,acid,

' under conditions adapted to.form an insoluble electrically conducting'film over any solder prescut on said surface.

"6. The method of preparing thesurface, which .is liable to poisoning against the receptionof an cent of phosphoric acid, under conditions'adapted to form an insoluble electricallyconducting film over any solder present on said surfaceand thereafter rinsing said surface with water.

7. The method of preparing a nickel surface, which is liable to poisoning against the reception of an adherentelectrodeposit by the presence of solder thereon, so that nickel deposited thereon will strongly adhere thereto,- which comprises subjecting the nickel surface totreatment as anode in a concentrated aqueous solution of sulfuric and phosphoric acids containing not less than one percent of phosphoric acid,-un'de'r conditions adapted to form an insoluble electrically conducting film over any solder which may be present on said surface.

8. Method of forming a structure composed in part of steel and in part of electrolytic metal chosen from the class consisting of iron and nickel, wherein'said two metals are in contact over only a portion of their adjacent surfaces, which comprises: imparting to the steel the desired form of the steel part of the-structure; attaching to the surface of the steel a body-of solder of the size and form and in the'location of the void desired between the parts of the finished structure; 'treating'the solder-steel surface anodically in a concentrated aqueous solution of sulfuric and phosphoric acids containing not less than one percent of phosphoric acid; rinsing said surface with water; electrodepositing the metal chosen from said class of iron and nickel on the anodically treated surface; and thereafter removing the solder by fusion to leave a void between parts of the surfaces of the steel and of the electrodeposited metal.

9. Process which comprises soldering a stainless steel form onto metal chosen from the class consisting of steel and nickel, anodically treating the composite surface of stainless steel, solder, and the said chosen metal in a concentrated aqueous solution of sulfuric and phosphoric acids containing not less than one percent of phosphoric acid, electrodepositing over said treated surface a metal chosen from the class of iron and nickel, unsoldering the stainless steel form from thesaid chosen metal and stripping it from the electrodeposit.

10.'Method of electrolytically patching holes in sheets formed of metal chosen from the class consisting of steel and nickel, which comprises bevelling the edges of the hole, soldering stainless steel across the bottom, cleaning all solder off that part of "the stainless steel exposed through the hole, cleaning the surfaces in and immediately surrounding the hole, treating said surfaces anodically in a concentrated aqueous solution of sulfuric and phosphoric acids con taining not less than one percent of phosphoric Number Name Date acid, electrodepositing a metal chosen from the 1,674,941 Bart June 26, 1928 class of iron and nickel over said area to a depth 1,793,936 Knauss Feb. 24, 1931 at least as great as the thickness of the sheet, 1,906,376 Holmes May 2, 1933 melting the solder, and stripping the stainless 5 2,132,438 Romig Oct. 11, 1938 steel from the surface of the electrodeposit. 2,299,054 Harshaw Oct. 13, 1942 WILLIAM B. STODDARD, JR. 2,334,699 Faust Nov. 23, 1943 2,457,061 McQuire Dec. 21, 1948 REFERENCES CITED f f d th 10 OTHER REFERENCES The fol-lowmg erences are 0 mm m 6 Metal Finishing, pages 306-312, June 1942 (an file of this patent.

article by Young et a1). UNITED STATES PATENTS Wein, Electroforming, Products Finishing, Number Name t pages 66, 68, August 1945.

1,455,023 MCCDI'd May 15, 1923 15 

1.IN PREPARATION FOR THE ELECTRODEPOSITION OF NICKEL ONTO A METALLIC SURFACE COMPOSED IN PART OF SOLDER AND PART OF A METAL CHOSEN FROM THE CLASS CONSISTING OF STEEL AND NICKEL, THE STEP OF FORMING ON AND CO-EXTENSIVE WITH THE SURFACE OF THE SOLDER, BY MAKING THE SURFACE ANODE IN A CONCENTRATED AQUEOUS SOLUTION OF SULPHURIC ACID AND PHOSPHORIC ACID AN ELECTRICALLY CONDUCTING FILM WHICH IS RESISTANT TO PENETRATION OR REMOVAL BY THE PLATING SOLUTION. 